U.S. Pat. No. 6,382,309 discloses a heat pipe assembly having an evaporator for vapor in a first casing, and a reservoir for condensate in a second casing. In addition to the space consumed by two casings, both casings are open one-to the-other and need to be hermetically sealed to support an evacuated internal environment. Combining the evaporator and reservoir would face the difficulty of combining vapor and condensate in the same casing, which would tend to cause thermal interaction of vapor and liquid. The heat transfer efficiency of the heat pipe would be reduced. Further, the flow loop of the heat pipe would be slowed by reduced vapor pressure and reduced liquid flow. Further, a combined evaporator and reservoir in the same casing would contribute further parasitic heating of the reservoir due to the industry known, heat leak problem associated with a loop heat pipe.